Restrictor tubing



May 7, 1940. J. KARMAZIN RESTRICTOR TUBING Filed may 18, 1936 I INVENTOR! Patented Ms; 1, 1940 RESTRICTOR TUBING .[ohn 'Karmalin, Huntington, Ind., assignor General Motors Corporation, Dayton, Ohio, a

corporation of Delaware Application May 18, 1936, Serial No. 80,255

1 Claim. (01. 1as 44) This invention relates to refrigerating apparatus. An object of this invention is to provide an improvement in refrigeration which includes a rel- 5 atively long and small diameter tube which is adapted to interpose the necessary restriction between the high side-and the low side of the refrigerating system.

Further objects and advantages of the pres- 10 ent invention will be apparent from the following description, reference being had to the accompanying drawing, wherein a preferred form of the present invention is clearly shown.

In the drawing:

18 Fig. 1 is a diagrammatic representation of arefrigerating apparatus embodying features of this invention; I

Fig. 2 is a view, partly in cross-section of a step in the manufacture of the tubing; N Fig. 3 is a view similar to Fig. 2, but showing a modified form of the invention; Fig. 4 is a view, partly in cross-section, of the tubing in partly finished form; and Fig. 5 is a diagrammatic view of a furnace in 38 which thetubing'may be heated and brazed.

I-Ieretofore tubes of small diameter'and relatively great length have been interposed between .the high side and the low side of a refrigerating system, as a substitute for automatic expan- 30 sion valves, floats and the like. However, these prior uses have been open to the objection that the tubing cannot be made of uniform diameter in large quantities so that a uniform product can be obtained in mass production.

According to this invention, however, a restric'tor tube is provided which interposes uniform restrictions on the flow of refrigerant and in which the tubing canbe manufactured in large quantities with absolute uniformity.

49 This invention is particularly applicable to refrigerating systems having high sides and low sides. The high side may include a compressor unit l discharging into a condenser unit H. The liquefied refrigerant then flows through the 45 restrictor tubing l2 to the evaporator l3. From thence the evaporated refrigerant returns through the pipe II to the compressor unit I.

In modern household refrigerators, the above system may take the specific form shown in the 0 drawing in that the compressor Ill includes a motor and compressor sealed within the casing IS. The condenser ll may include a series of loops through which air is circulated by means of the motor fan IS. The condensed refrigerant ll is gathered in the receiver ll. The tube I2 may be of uniform dimensions throughout its length,

and, if excessively long, may be coiled at i8.

Theevaporator I 3 may be-provided with one or more freezing shelveslS having passageways 20 through which the refrigerant flows before it enters a lower header 2| which distributes refrigerant to the upwardly directed loops 22 discharging into headers 23 which are joined by the branches 24 discharging into the pipe ll.

The motor-compressor unit Ill generally includes a type of motor which runs at a constant speed whereas the condenser II is subject to varying degrees of cooling depending on the temperature of the atmospheric air flowing through the condenser. On a. cool day therefore, the condenser ll operates at a relatively cool temperature and the refrigerant pressure on the high side of the system is relatively low. On warm days, on the other hand, the refrigerant pressure is relatively high on the high side. The tendency,'therefore, is to cause too much refrigerant to flow through the restrictnr I! on warm days, and if the tube is not properly calibrated, the liquid refrigerant in the receiver I1 is emptied and gaseous refrigerant tends to flow through the tube l2. When this occurs, the efilciency of the refrigerating apparatus is greatly lessened with consequent high current consumption for the refrigeration produced.

. It is well-known that if tubes of proper length and cross-section are provided, the restriction of the tube II can be properly balanced so that this flow of gaseous refrigerant can be avoided and yet a sufflcient flow of liquid refrigerant can be insured at all room temperatures for'the refrigeration demands. In ordinary household refrigerators, a tube of about .035" internal diameter and from 10 to 14ft. in length has been found satisfactory. However, it is extremely difficult to manufacture a tube of such small internal diameter in large quantities for installation in a cabinet or the like. According to my invention atube is provided which imposes a more uniform restriction and which may be cheaply manufactured in large quantities.

In manufacturing my tubing, steel wire of from .018 to .023" in diameter is wound on the rotating member of the usual spring coil machine to produce a wire coil in which the individual loops 3| are placed under" natural tension tending to hold them together. Thereafter,-

a. wire 32 of bonding material is placed in the spring tube and the sameis passed through a heating zone or furnace 33 in which a reducing atmosphere, such as hydrogen, is maintained.

The tube is heated to a temperature sumcient to cause-the copper wire I! to flow into the interstices 34 between the loops3l and braze the same together hermetically. Preferably the tube is maintained in a horizontal position through the heating zone and yet the bondin material or copper from the wire 321 rises by capillary attraction between the loops 3| and brazes the entire tube. The tendency is to provide a tube which is thoroughly copper coated both inside and outside throughout its area. This produces a very clean tube of uniform restriction.

In order to provide a tube which may be even more readily bent, I may wind two or more steel wires 35 and 36 on the coil machine 31 to pro-' duce the spring coil 38. At the same time a reinforcing wire 39 is wound over the wires 35 and 33. This wire 33, however, may be omitted if desired. By winding the two wires "and 33 the loops of the wires are at a more acute angle and the tube, after it has been brazed in the same manner as the tube 3|, is very easily bent without. danger of rupture. It is to be understood, that the tube made in accordance with Fig. 3, is brazed in the same manner as that described ior the tube shown in Fig. 2.

The internal spiral ridges formed by my tubing provide a more efficient restricting action than a tube of smooth internal bore. Oil slugs, which generally are present in refrigerating sys- 2,1eaea1 tems 01' this kind, are forced more easily through the tubing. These ridges also tend to provide a more efllcient restriction against the flow of gas through the tubing and thustendsto preventloss of eiliciency in this respect.

While I have described the tubing as made of steel wire bonded together with copper, it. is to be understood that other materials may be used for the same purpose. Thus the wires-which form the loops of the tube may be of copper, and

"the bonding material may be any or the wellknown solders adapted to bondcopper. Such solders may be in the form of wire if desired.

While the form of embodiment of the inventionas herein disclosed, constitutes a preferred form, it is to be understood that other forms mightbe adopted, all coming within the scope oi. the claim which follows.

JOHN KARMAZIN. so 

